Protective effect of 3-O-methyl quercetin and kaempferol from Semecarpus anacardium against H2O2 induced cytotoxicity in lung and liver cells

BACKGROUND Hydrogen peroxide is continuously generated in living cells through metabolic pathways and serves as a source of reactive oxygen species. Beyond the threshold level, it damages cells and causes several human disorders, including cancer. METHODS Effect of isolated 3-O-methyl quercetin and kaempferol on H2O2 induced cytotoxicity, ROS formation, plasma membrane damage, loss of mitochondrial membrane potential, DNA damage was evaluated in normal liver and lung cells. The RT-PCR analysis used to determine Nrf 2 gene expression. Calorimetric ELISA was used to determine Nrf2 and p-38 levels. Expression of SOD and catalase was analyzed by Western blot analysis. RESULTS The present study isolated 3-O-methyl quercetin and kaempferol from the stem bark. They protected normal lung and liver cells from H2O2 induced cytotoxicity, ROS formation, membrane damage and DNA damage. Pre-treatment with 3-O-methyl quercetin and kaempferol caused translocation of Nrf2 from cytosol to nucleus. It also increased expression of p-p38, Nrf2, SOD and catalase in H2O2 treated lung and liver cells. CONCLUSION The flavonoids isolated from S. anacardium significantly reduced H2O2 induced stress and increased expression of Nrf2, catalase and superoxide dismutase-2 indicating cytoprotective nature of 3-O-methylquercetin and kaempferol.